Method of manufacturing turbine or the like blades



June 22, 1954 F w wHlTEHEAD 2,681,500

METHOD OF MANUFACTURING TURBINE OR THE LIKE BLADES Filed July 3] 1950 2 Sheets-Sheet 1 INYENTOK F? W. WHH'EHEAD June 22, 1954 F. w. WHITEHEAD 2,681,500

METHOD OF MANUFACTURING TURBINE OR THE LIKE BLADES Filed July 3, 1950 2 Sheets-Sheet 2 F'JZ? 17K? 0 4 7 &

INVENTOK F. w. WHH'E HEAD E WMwP m-IQ\ MEGS.

Patented June 22, 1954 METHOD OF MANUFACTURING TURBINE OR THE LIKE BLADES Frederick William Whitehead, Bristol, England, assignor to The Bristol Aeroplane Company Limited, Bristol, England, a British company Application July 3, 1950, Serial No. 171,958

Claims priority, application Great Britain July 18, 1949 3 Claims.

This invention concerns methods of manufacturing turbine or the like blades (more particularly for gas turbine engines) having a shroud which form a part of a built-up shroud ring when the blades are assembled side by side. For convenience such blades are referred to hereinafter as shrouded blades.

There are, broadly speaking, two main types of blades, namely, solid blades and hollow blades,

the former being characterised by a substantially solid vane portion (though it may have relatively small channels or passages extending therethrough) and the latter being characterised by a vane having a relatively thin wall, for example, being fabricated from sheet metal. The present invention is concerned with solid blades as just defined (hereinafter referred to throughout the specification simply as solid blades) and does not relate to hollow blades.

The present invention has for its object to provide an improved method of making shrouded blades where it is impossible or inconvenient to form the shroud when producing the blade shank.

More specifically this invention has for its object to form a shroud on the concave face of a blade subsequently to the production of said face.

A further object of the invention is the provision of a shroud on the concave face of the blade which is integral with the blade shank i. e. is not separately formed and subsequently united to the blade by welding or in any other way.

According to the present invention a method of manufacturing shrouded, solid, metal blades of aerofoil shape in cross section comprises bending over the tip end of the blade and forming a shroud or a part of a shroud from the bent-over portion.

The blade may be rough machined or finish machined prior to bending the tip end to form the shroud and the term machined blade as used hereinafter is to be understood as including both the partly and completely machined blade.

According to a feature of the present invention a method of manufacturing shrouded, solid, metal blades of aerofoil shape in cross section comprises forming a shroud portion integral with, and projecting substantially at right angles to, the convex surface inwardly of the tip of the blade at the same time as said surface is produced,

forming a concave surface which extends beyond a said shroud portion to form a tip portion of the blade, bending the tip portion to lie substantially in the plane of said shroud portion and projecting from the concave surface and shaping the bent-over tip portion and said shroud portion to form a. blade shroud.

In a gas turbine engine the thermal and mechanical stresses in the blades greatly limit the range of materials which may be used in making the blades. In order to achieve the required mechanical strength the blades may be machined from a solid work-piece-either from a bar of material or from forging.

In the specification accompanying application No. 7,50l/e7 there is described a machine for forming the convex surface of a turbine blade from a bar of material and in the specification accompanying application No. 7,828/47 there is described a machine for producing the concave face of unshrouded blades from a bar of material. Ihe present invention makes use of the machines described in said applications and is concerned with forming a shroud from the machined blade by bending the tip end of the blade and thereafter shaping it in any convenient manner to the form required for the blade shroud.

Practical applications of the present invention will now be described, by way of example only, with reference to the accompanying drawings,

whereof:

Figure 1 is a diagrammatic sectional elevation of the means for forming the concave face of a solid, metal blade of aerofoil shape in cross section,

Figure 2 is a plan view of Figure 1,

Figure 3 is a diagrammatic sectional elevation of the means for forming the convex surface of a solid metal blade of aerofoil shape in cross section,

Figure 4 is a plan view of Figure 3,

Figures 5, 6, '7, 8 and 9 show various steps in the formation of the shroud by bending and shaping the tip of the blade,

Figures 10 and 11 show two steps in the formation of an alternative construction of shroud by bending and shaping the tip of the blade, and

Figure 12 is a side View of a finished blade made as described with reference to Figures 1-9 of the drawings.

Referring to Figure 1, the blade is produced from a bar of material 20 which is suitably held in a carrier generally indicated at 2 I. To impart the required shape to the concave surface of the blade there is provided a cutter or a grinding wheel 22 which is carried and driven by a shaft 23.

The grinding wheel or cutter 22 is of conical form and is fed into the blade in the direction of the arrow .24 and having completed this movement the wheel is then moved across the blade in a transverse direction about an axis 25 (Figure 2) which is inclined with respect to the axis of rotation of the shaft 23 i. e. the wheel or cutthen mounted on a machine to form the con-' vex surface 28. The machine for-forming the convex surface is diagrammatically illustrated V in Figures 3 and 4 to which reference will now made. The bar 26 is held in a carrier 29 so that it is movable in the direction of arrow 3| to engage a grinding wheel 30. The grinding wheel 35 has a face width less than the height of the bar and is mounted on a shaft 33 the axis of rotation of which is approximately parallel to the longitudinal axis of the bar 20. The carrier is is supported by a shaft 34 which is rotatably mounted in bearings 35 and there is a handle 36 for oscillating the shaft and hence the carrier 29. The assembly of the carrier 29 and its driving means is mounted on a slide 3'! for movement towards and away from the grinding wheel as. The shaft 36 carries a cam 38 which engages a follower 39 carried by a frame member 49. A spring 4| is provided to hold the cam in engagement with the follower 39 and to draw the bar towards the grinding wheels 36, 3|. The machine shown in Figures 3 and i is more fully described in the specification accompanying aplication No. 7,501/4'7 and it is to be understood in' the accompanying drawings the machine is diagrammatically shown.

While the grinding wheel se is being driven the handle 36 is oscillated whereby the 'bar 20 is oscillated in the direction of arrow d3 about axis' i4 and, at the same time is reciprocated relatively to the grinding wheel 30, in the direction of arrow 45 so that the required convex surface 28 is formed on the bar.

left for a final machining operation after the shroud has been formed as will shortly be described.

The form of the blade produced by the machining operations described above will be apparent from Figure and it willbe noted that the bar 29 has been formed with a blade shank 4 5 having concave and convex surfaces 25, 28 respectively. The bar 26 will subsequently be machined to form the blade attachment portion. It is to be understood that the method and apparatus for forming the concave and convex surfaces described are given by way of example only and other procedures may be followed.

As shown in Figure 5 the blade is gripped between anvil members 4?, 33 which are accurately shaped to fit the surfaces 26, 28 respectively. The members 41, '48 are carried by any convenient form .of adjustable gripping device 49. The tip portion of the blade is heated either before it is clamped between theanvil members M, 68 or, as shown in Figure 5, while it is so held. The tip portion of the blade is then hot forged so that it is bent onto the surface 50 of the anvil member i'l. The surface 50 is shaped so that with the hot forging operation'that part of theltip 4 portion 21 which is engaged thereby will have the required shape imparted to it. Figure 7 shows the tip portion 21 at the end of the hot forging operation and it will be noted that it has been bent over so as to lie substantially in the plane of the shroud #2. Following the hot' forging operation the edges of the parts 21 and 32 are ground as shown in Figure 8. The edges 5| are shaped by a grinding wheel 52 and the edges 53, 5d are similarly shaped by a grinding wheel 55.

peripheral surface '56 is ground by wheel 51 to the required cylindrical curvature.

The final product (Figure 12) is a blade having a shroud 53 which is made up from the tip portion 2i and the shroud portion 52 both of which are integral with the blade shank at.

In the alternative arrangement shown in Figures l0 and 11 the concave surface is formed as described with reference to Figures 1 and 2. The convex surface is formed generally as described with reference to Figures 3 and 4 with, however, a single grinding wheel so that the shroud 4'2 is not produced. The tip portion of the blade 2! is longer than in the construction shown in Figure 5. The tip portion 2'! is hot forged in the manner described above and is thereafter ground to final shape and the shroud Gel which is finally produced extends entirely to one side of the blade shank 4S and is of such length as to abut the tip end of the shank 48 when the blades are mounted in the turbine.

Although it is preferred that a hot forging operation be used to bend over the tip of the blade, this may bedone by a cold forging operation.

Furthermore, althoughthe operation of bending over the tip of the blade has been satisfactorily carried out by hand hammering, it is to be understood that the tip of a blade may be automatically bent in a machine.

I claim:

l. A method of manufacturing shrouded, solid, metal blades of aerofoil shape in cross-section which comprises securing a blade blank at one end, grinding the blank to form the convex and concave sides of the blade, the shape of the concave surface so produced extending to the free end of the blank, machining the free end of the blank on the convex side of the blade to form an extended tip portion of the blade and a shroud projecting substantially at right angles from the convex side of the blade, subjecting said tip portion to a hot forging process, whereby said tip portion is bent over to lie substantially in the plane of said shroud portion and projecting from said concave surface to form with the shroud portion a shroud for the blade, the underside of said bent over tip portion being shaped durform a convex side of the blade extending from the root to a point short of the free end of the blade, whereby a thickened tip portion is left at the free end having a concave surface produced as a continuation of said concave surface of the blade, removing a part of the thickenedtip portion on the convex side of the blankto form the Referring to Figure 9, the blade is thereafter suitably mounted so that the outer tip of the blade and a shroud portion integral with and projecting substantially at right angles from the convex side of the blade, bending over said blade tip to lie substantially in the plane of said shroud portion and projecting from said concave side of the blade, and shaping the bentover blade tip and said shroud portion to form the blade shroud.

3. A method of manufacturing shrouded, solid, metal blades of aerofoil shape in cross-section which comprises machining a blank on opposite sides to form the convex and concave sides of the blade, so that the concave side extends from the root to the free end of the blade and the convex side extends from the root to a point short of the free end of the blade, whereby a thickened portion is left at the free end, machining the thickened portion of the blank at the free end of the blade and on the convex side to form an extended tip portion of the blade having a concave surface formed as a continuation of the concave surface of the blade and leaving a shroud portion projecting substantially at right angles from the convex side of the blade, bending over said tip portion to lie substantially in the plane of said shroud portion and projecting from said concave surface of the blade, and shaping the bent over tip portion and the shroud portion to form the blade shroud.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 255,329 Parry Mar. 21, 1882 819,106 Wilkinson May 1, 1902 1,073,623 Owen Sept. 23, 1913 1,286,283 Gilson Dec. 3, 1918 1,910,943 Wiberg -1 May 23, 1933 2,373,827 Halford Apr. 17, 1945 2,593,139 Greenshields Apr. 15, 1952 FOREIGN PATENTS Number Country Date 169,913 Great Britain Oct. 13, 1921 

